Method of removing free sulphur from grease



Patented Nov. 17, 1925.

UNITED STATES 1,561,911 PATENT'OFFICE.

HUGH CHRISTISON, OF METHUEN, MASSACHUSETTS, AND CLARENCE L. NUTTING, OI? SALEM, NEW HAMPSHIRE. ASSIGNORS TO ARLINGTON MILLS, OF LAWRENCE, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

METHOD OF REMOVING FREE SULPHUR FROM GREASE.

No Drawing.

The grease contained in raw wool is inti-" mately associated with some sulphur which is practically in such an elementary state as to behave as if chemically free; and when the grease in this condition is extracted from the raw wool without undergoing sub stantial change in its constitution,'as may be done by employing for that purpose the naphtha solvent process, the free sulphur therein although-present in relatively small quantity is sufiicient to detract seriously, in certain cases, from the utility otherwise possessed by the grease itself.

The object of our invention therefore, is to remove from such grease or from any similar fatty matter in like manner circumstanced, the free sulphur associated therewith without injuriously affecting the useful qualities of the grease itself. k

This result we accomplish by heating and preferably by boiling with accompanying agitation, the crude sulphur-containing grease in an aqueous solution of an alkali compound'which under these conditions is capable of chemically taking up such sulphur to form therewith another water soluble compound, or other water soluble com pounds, having the like alkali as its base, or as their bases, and by subsequently ob- Y taining the purified grease by physical application of gravitative or centrifugal force to its mixture with the liquor constituted by' the water holding in solution the alkali-sulphur compound or compounds formed as aforesaid, together with any other soluble residual matter incidentally present, whereby the separation of such grease and liquor is effected because of their differences in specific gravity.

Our invention may be best exemplified by the following efficient and satisfactory mode of procedure:

Application filed June 3,1921. Serial No. 474,850.

Into a boiler-tank, preferably heated by asteam-coil which is provided with open jets, we introduce a volume of water equal to about twice, the volume of grease to be treated; and when this water is hot we dissolve therein, for every pound of free sulphur contained in the grease, six' pounds of sodium sulphite technically known as normal sodium sulphite. The crude grease in a melted state is then added to this solution and the whole batch thus constituted is boiled. for half an hour while being agitated meantime either by the passage of live steam through it or by mechanical means. During this boiling the sodium sulphite combines with the free sulphur. associated with the grease and is thereby converted into sodium thiosulphate which likewise remains dissolved in the water present.

WVhen the boiling has ceased and the resulting emulsion is allowed to stand undisturbed the water with its soluble ingredients tends to gravitate out of it gradually and to settle below the grease from which such settled liquor may finally be drawn off. This separation is expedited by keeping the contents of the tank at a temperature as high as feasible without promoting the agitation accompanying boiling, and it is convenient to have the tank steam-jacketed for the purpose. Or better still, becausecapable of being accomplished in less time, the separation of the liquor from the grease may be effected by introducing the emulsion as hot as practicable into a centrifuge similar in construction and mode of operation to the well known machine for separating cream from milk by centrifugal action.

Furthermore such separation by either. of

these means is also facilitated'and accelerblowing into it sulphur dioxide gas through.

the open jets of the coil previously used for steam heating, sufiicient in quantity to cause the emulsion to yield an acidtest to blue litmus paper.

But a persistent difiiculty stands in th way of expeditiously separating from the grease the entire aqueous solution constituting the treating liquor in its ultimate state,

owing to the fact that the grease itself ab-- sorbs a notable quantity of water which will not readily separate therefrom and which consequently in this case retains a proportionate amount of the soluble contents of the liquor whereof it is a fractional part. Hence in order to reduce to a negligible quantity the remnant of sulphur compounds retained with the water thus absorbed, the grease, after the separation therefrom of SO much of the said liquor as can be first eliminated, needs to be subjected to successive aqueous washings and drainings. This further treatment may preferably be accomplished by employing for each of such subsequent washings a hot dilute solution of sodium chloride in water which is likewise then allowed to settle and run off, or is introduced into a centrifuge to effect an equivalent result, and finally the grease thus puri fied is dehydrated to substantially the minimum of its water of absorption, either by having hot air blowfithrough itor by submitting it to the mechanical action of a centrifugal separator.

Although according to established chemical relations one pound of free sulphur requires no more than four pounds of sodium sulphite to exhaust it in combining there-- with to form sodium thiosulphate, yet experience has shown that in practising our invention the best results are obtained when provision is'made for the presence in the treating liquor of as much as one hundred and fifty per cent of the amount of'sodium sulphite theoretically needed for conversion into sodium thiosulphate by combination with all the free sulphur contained in the grease to be treated. This excess is highly desirable because without it there would apparently bedifiiculty in bringing about a reaction thorough enough to induce all of the free sulphur present in the grease undergoing treatment-to enter into chemical combination, and at any rate because such complete exhaustion of the free sul hur would unduly prolong the operation 0 the process if much less additional sodium sulphite were used, notwithstanding that a corresponding surplus of the latter must remain unchanged in the liquor ultimately separated from the grease.

The process already hereinbefore specifically described may be practised in a somewhat" indirect mode by the preliminary employment of certain chemical reagents which upon being brought together in aqueous solution under suitable conditions result in the ultimate production of a liquor containing sodium sul bite and likewise capable'of being used or the treatment of sulphur-containing grease to eflect its purification.

accordance with either of the following recipes designated respectively A, B, C and D, to wit:

A. 57 pounds of sodium hydroxide, commonly known as caustic soda, together with 450 pounds of commercial bisulphite of soda solution which usually contains about twenty per cent in weight of sulphur dioxide, are dissolved in 80 gallons of hot water.

13.11% pounds of sodium hydroxide are dissolved in 120 gallons of hot water, and to this solution are added 91 pounds of sulphur dioxide gas by being blown into it through a suitable perforated coil of pipe.

C. pounds of anhydrous sodium carbonate, or else 120 pounds of sodium bicarbonate, are dissolved in gallons of hot water and to either of these solutions are added 450 pounds of commercial bisulphite of soda solution constituted as aforesaid.

D. 150 pounds of anhydrous sodium carbonate, or else 240 pounds of sodium bicarbonate, are dissolved in 120 gallons of hot water, and to either of these solutions are added 91 pounds of sulphur dioxide gas by being blown into it in the manner aforesaid.

Other sodium salts formed by combination with acids which are respectively soluble in water and weaker than sulphurous acid, such as for example tri-sodium phosphate, may be substituted in proper quantity for sodium carbonate or bicarbonate in either of the foregoing recipes designated C and D.

Precaution should be taken that the liquid prepared in accordance with either oftheserecipes suitable for employment in the practise of our invention by indirect mode of procedure does not show an acid reaction when tested with litmus paper. If it should should approximate as nearly as possible to that of the liquor produced by dissolving in hot water at the outset neutral sodium sulphite already formed, as in the direct mode of procedure first .hereinabove described. a

Into the liquor resulting from conformity to either of the foregoing recipes designated as suitable for pursuing an-indirect mode of procedure, the one thousand pounds of grease containing .three per cent-in weight of free sulphur already mentioned are introduced and thereupon the whole batch thus constituted is kept boilin and agitated for half an hour during w llCh operation the sodium sulphite resulting fromthe chemical reactions of the ingredients originally brought together in solution according diam thiosulphate by combining with the fredsulphur contained in the grease, as far as the quantity of such free sulphur suflices for that combination.

The subsequent steps of the process are those which succeed to the corresponding stage of what constitutes the direct mode of procedure first hereinabove described.

Theoretically and doubtless actually in the course of the chemical reactions in-' volved in realizing each of the several modes of procedure herein set forth to ex- .emplify our invention, sodium sulphite is the preponderant reagent by means of which the free sulphur originally contained in the grease is ultimately incorporated and sodium thiosulphate the principal resultant product of such incorporation; but-thc prolonged duration of the process in each instance tends to induce between the constituent ingredients of the treating liquorvarious further chemical reactions which probably result in the formation of relatively small quantities of dithionic, trithionic, tetrathionic or pentathionic acid and of corresponding sodium polythionates. Such additional variant compounds however like the sodium thiosulphate will have been produced at the expense of the free sulphur eliminated from the grease, and will have been dissolved in the water of the treating liquor ultimately separated from the grease thus purified.

' Thus far, sodium has been the only baseforming element specifically mentioned in connection with the chemical compounds employed and produced in the aqueous solution with which the grease containing free sulphur is treated in the described modes of I procedure embraced in our invention; and sodium is practically the most availablebase-forming element for such industrial purposes; but it should be understood that the corresponding compounds of potassium and ammonium are equivalent substitutes therefor.

lVe claim:

1. The method of removing free sulphur from grease by heating and simultaneously agitating their mixture with an aqueous solution of a neutral alkali-sulphite in sufficient quantity to exhaust such free sulphur by chemically uniting therewith to become converted into a thiosulphate of the same alkali, and by subsequently separating the grease from the water holding in solution the alkali-thiosulphate thus formed, by means adapted to effect their assumption of relative positions according to their respective differences in specific gravity.

2. The method of removing free sulphur from grease by boiling and agitating their cording to their respective differences in specific gravity.

The method of removing free sulphur from grease by heating and simultaneously agitating their mixture with an aqueous solution of a neutral alkali-sulphite in quantity somewhat more than theoretically sufficient to exhaust such free sulphur by chemically uniting therewith, and by subsequently separating the grease from. the water holding in solution the resulting and residual alkali-compounds, by means adapted to effect their assumption of relative positions according to their respective differences in specific gravity.

4, The method of removing free sulphur from grease by boiling and agitating their mixture with an aqueous solution of neutral sodium sulphite in quantity somewhat more than theoretically sufiicient to exhaust such free sulphur by chemically uniting therewith, and by subsequently separating the grease from the water holding in solution the resulting and residual sodium compounds, by means adapted to effect their assumption of relative positions according to their respective differences in specific gravity.

5. The method of removing free sulphur from grease, by heating and simultaneously agitating their mixture with an aqueous solution of a neutral alkali sulphite in sufficient quantity to exhaust such free sulphur by chemically uniting therewith, and therewith sulphurous acid the emulsion resulting from this purifying treatment of the grease, in order to facilitate its separability from the treating liquor and the soluble contents thereof. j

HUGH- CHRISTISON. CLARENCE L. NUTTING.

Certificate of Correction.

' It is hereby certified that in Letters Patent No. 1,561,911, granted November 17, 1925, upon theepplication of Hugh Christison, of Methuen, Massachusetts, and

ClarenoeL. Nutting, of Salem, New Hampshire, for Methods of Removing Free Sul hur from Grease, an error appears in the printed specification requiring correetlfon as follows: Page 3, line 116, claim 6, for the word solidifying 'read (width mg; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 15th day of December, A. D. 1925. i [snub] WM. A. KINNAN,

' Acting 0ommz'8s'ioner of Patents. 

